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R/C Newbie

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I have a 2S lipo that swelled up and split the hard case I wrapped it with tape and seems to work fine and charge fine but its is just swollen. I hooked it to my little tester do these reading look correct for a 2S 7.4v battery? If not what should they be?

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R/C Newbie

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Thanks for the help. This is the 3rd batteryt I have had this happen with not having good luck get like 15 charges and then won't charge or swells up
 

Lazy Bushman

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Mate chuck the batteries. Once the swell your risk of catastrophe is substantially higher, just google Lipo batter fire.

I don't know your situation or the vehicles you are running them in but the following are things to be careful of with Lipo's;
  • Don't charge at a rate higher than recommended by the manufacturer. A lot now do 2C but always check. Sing out if you don't know what I'm talking about but for example a 4000 Mah battery 1c= 4amps, 2c=8maps etc
  • Don't run them flat. Check you have the LVC (Low voltage control) set correctly on your vehicle. If you don't have LVC then get one of those little alarms that cost about $5 which plug in to the balance cable. It will sound a warning when voltage is low.
  • Use a smart charger. You probably are but you want to just make sure you aren't over charging the batteries
  • Don't store them in hot places eg don't leave them in your car
  • When you aren't using your batteries make sure you do a Storage Charge prior to putting them away.
Assuming you aren't dropping on concrete on a regular basis, these are the main points to remember. A good Lipo that is looked after should give you a couple of thousand cycles in theory before going bad. In a basher the batteries do cop a bit of a pounding so it would unlikely to get that kind of life but it is possible.

Lastly all my batteries are hard cased to provide a little more protection. A lot of people run soft packs and have no issue, but I run the hard packs.
 

Heisenburg

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Always unplug the packs when not in use. Most ESCs have a slight draw, even when switched off. Keep the packs at 50% charge at rest, and only charge to full when you anticipate running them. Once a week, I use the STORE function on my Traxxas ID charger to bring it up to 50%, or discharge it to 50%.
 

Sledgehog

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As Lazy Bushman said... dispose of the battery (properly). The cost of any lipo is nothing compared to injury or fire.
 

olds97_lss

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4.2V is full. Then discharging a bit uneven seems to be relatively normal, it's why we balance charge them back up so as not to drive one cell higher than another.

What brand of battery? What rate of charge are you using? What's your LVC set to in the vehicles?

Out of 30 or so lipo's, I've had one "swell" to an unusable point. It was a traxxas 5000mah 3S. A few of my older 2S 9000mah lipo's have swelled a very little bit after 4 months or so of use and never really got worse over the following year after that, but one did drop a cell.
 

HeavyBag

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When my last 3S pack started to puff, noticing after a run, I let it cool down, and put the cells at storage voltage. When the cells reached storage voltage, I then tried charging the 3S pack. Well, during the charge, the top cell (puffed cell) heated up more than the rest of the pack. At least I could tell a difference between the top and bottom cells. That was enough for me to call it quits for that pack. I wasn't taking any chances. Put my 20 amp discharger on the pack and got rid of it. During the discharge, it didn't take long for the cell to heat up and puff to extreme size...started venting (from fully charged state) in about 4 minutes.
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My next 3S pack will definitely be one with a higher C rating.
 

Lazy Bushman

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The C rating won’t do anything to save your battery. It is simply the calculation factor to determine the max constant current draw your battery can handle.
 

Peeeenuuutt

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And something I’ve learned over the years... 1c is the max charge rate on any lipo. If it says 2c it’s lying. Really does damage them right the hell up.
 

Lazy Bushman

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I use 2c where it is recommended by the manufacturer and 1c where no recommendation is made. 1c is the safest to be sure. The issue has more to do the the other materials in the battery opposed to the lithium itself.

I don’t know the answer to this question, but I have never really understood the reason behind 1c/2c/etc for charging and discharging. At the end of the day it is about the amount of current running into and out of the battery and when running in your RC car it certainly is discharging at a rate higher than 2c (usually double digits)....like I said I don't know the answer, maybe someone here does
 

Peeeenuuutt

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I use 2c where it is recommended by the manufacturer and 1c where no recommendation is made. 1c is the safest to be sure. The issue has more to do the the other materials in the battery opposed to the lithium itself.

I don’t know the answer to this question, but I have never really understood the reason behind 1c/2c/etc for charging and discharging. At the end of the day it is about the amount of current running into and out of the battery and when running in your RC car it certainly is discharging at a rate higher than 2c (usually double digits)....like I said I don't know the answer, maybe someone here does
Simple. I’ll break it down. Battery molecules change when you charge them, creates energy. The faster you charge, the quicker the transition. If you rush it, you get failure, which is hydrogen (puffing). That’s why charging slower is always better.
 

HeavyBag

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The C rating won’t do anything to save your battery. It is simply the calculation factor to determine the max constant current draw your battery can handle.
My current pack(s) run a lot warmer than the higher C rated packs I used to use.
 

Lazy Bushman

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There are a number of possible reasons for that but you would hope that the higher rated C batteries have better thermal protection and more conductive internally which would help keep them cooler.
 

olds97_lss

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The C rating won’t do anything to save your battery. It is simply the calculation factor to determine the max constant current draw your battery can handle.
The way you worded that is kind of misleading.

A higher c-rating does mean it's capable of higher amperage draw safely. Albeit some (likely many) are highly inflated for marketing purposes.

I don't fully grasp why the "c rating" system even exists. Why they aren't just labeled in constant amps and max amps doesn't make a lot of sense to me. C rating is just one more thing to confuse/obfuscate what a pack is capable of.
 

Lazy Bushman

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Yes @olds97_lss you are right. What I was meaning, and perhaps it hasn't come across correctly, or it did and I'm just wrong. My intent was to say that having a higher C rating doesn't provide greater protection against battery failure like over charging, over discharging etc. I reckon he could have had the same issue if @HeavyBag was using a 35C or 50C battery but it is speculation by me sitting on this side of the world.

As you correctly point out the higher c-rating is supposed to mean that the battery can support a higher maximum draw rate that when calculated is higher than many of the ESC's out there can handle anyway. The higher C rated battery should, in theory, have better thermals to support the extra draw that would translate to better heat management when in use......opposed to on the dash or a car :D
 

olds97_lss

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What I was meaning, and perhaps it hasn't come across correctly, or it did and I'm just wrong. My intent was to say that having a higher C rating doesn't provide greater protection against battery failure like over charging, over discharging etc.
I get you now. Yep, I'm with you on that. 20C or 100C, jab them with a screwdriver, they both explode. :)

The way I read what you posted earlier was that the "c rating" didn't mean anything regarding how the pack could supply power. Kind of threw me for a loop there as I know from reading your other posts that it was likely not what you meant. Just wanted to make sure.
 

Lazy Bushman

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All good mate. If you read it diff to how I meant it, that means others too probably will, so thanks for pulling it up. I’d rather be corrected than propagate miss information
 

LibertyMKiii

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I have a 2S lipo that swelled up and split the hard case I wrapped it with tape and seems to work fine and charge fine but its is just swollen. I hooked it to my little tester do these reading look correct for a 2S 7.4v battery? If not what should they be?

View attachment 119156View attachment 119157View attachment 119158
I saw storage voltage mentioned in the thread, but want to make sure this comes across clear for any LiPo newbs.
LiPos are interesting batteries that do not behave like any others you have used in the past.

2 cell 7.4v pack fully charged is 8.4Volts

Fully charged cells are 4.2 volts = unstable/dangerous
Low voltage is considered anything around 3.2 to 3.6V per cell = unstable/dangerous
Storage voltage is in the range of 3.82-3.86v per cell = stable/safe (sort-of)

Any time you are not going to use the battery over the next day or 2 it should be put in storage voltage. Always kept in a climate controlled room(I utilize our laundry room away from all bedrooms). Ideally should be kept in a LiPo safe bag, ammunition case, or steel tool box. They don't like heat or cold either.

A pack can be run with some swell but once its bad enough to crack a hard case it is time to fully discharge and toss it. I use a small DC fan to fully discharge my packs.
 

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